1. Field of the Invention
The present invention relates to an insulating film forming composition and an electronic device, more specifically, a production process of a composition for forming an insulating film excellent in film properties such as dielectric constant, mechanical strength, and heat resistance and used for electronic devices. The invention also pertains to an insulating film forming composition produced by the above-described production process, and an electronic device having an insulating film available using the composition.
2. Description of the Related Art
With the recent progress of high integration, multifunction and high performance in semiconductor integrated circuits (ICs), circuit resistance and interconnect capacitance have increased, leading to an increase in power consumption and delay time. Particularly, an increase of delay time has caused a reduction of signal speed and generation of crosstalk in semiconductor integrated circuits so that a reduction of interconnect resistance and parasitic capacitance is required in order to decrease this delay time and accelerate the speed of the semiconductor integrated circuits. As one concrete measure for reducing this parasitic capacitance, an attempt has been made to cover the periphery of interconnects with a low-dielectric-constant insulating film. In addition, this insulating film is required to have heat resistance high enough to withstand a thin film formation step at the time of producing a mounting board and post steps such as chip connection and pin insertion and also chemical resistance high enough to withstand a wet process. Moreover, Al interconnects have recently been replaced by low resistance Cu interconnects and it is therefore common practice to carry out planarization by CMP (chemical mechanical polishing). The insulating film is therefore required to have mechanical resistance high enough to withstand this process.
As an insulating film for covering the periphery of an interconnect, silicon dioxide (SiO2, k=3.9) has conventionally been used. However, use of a spin-coated insulating film having a relatively easily controllable film structure is now investigated for reducing a dielectric constant of an insulating film. Insulating film forming materials are disclosed, for example, in Japanese Patent Laid-Open No. 2003-176352, U.S. Pat. No. 5,965,679, Japanese Patent Laid-Open No. 2006-233128, Japanese Patent Laid-Open No. 2006-265513, and Japanese Patent Laid-Open No. 2007-119706.
On the other hand, insulating films to be used in semiconductor devices must have a stable dielectric constant even after film formation. For example, a gradual increase in the dielectric constant of a coated film due to absorption of environmental moisture after film formation is not preferred because it adversely affects the performance of semiconductor devices manufactured using such a film. In such a case, it is indispensable to evaporate water absorbed into the film by carrying out heat treatment subsequent to an insulating film forming step to restore the original dielectric constant. In the above-described insulating film forming materials, however, their dielectric constant may rise with the passage of time after film formation so that there is a room for further improvement of a dielectric constant restoration property by heat treatment.